The invention relates to a steering gear mechanism for a vehicle.
Conventional steering gear mechanisms for vehicles comprise a steering housing and a steering input shaft. The steering housing is sealed and has a receptacle through which the steering input shaft passes into the steering housing. The receptacle is sealed against the steering input shaft.
The steering input shaft of the steering gear mechanism is used to transmit the steering movement of the steering wheel onto the steering linkage. On the steering linkage, for example a steering rack is provided that can be engaged by a gear connected to the steering input shaft. In order to protect the steering gear mechanism from external influences such as for example dirt or humidity, it is sealed. To this end, on the one hand the through-passage of the steering input shaft into the steering housing is sealed, but also the output side of the steering housing is sealed, for example by means of bellows which are fixed to the steering housing and to a gearing rack and which can yield in a flexible manner during a movement of the gearing rack in the longitudinal direction, so that a reliable seal of the steering housing is ensured even during a movement of the steering rack.
However, as a result of temperature fluctuations or other environmental effects, the pressure within the steering housing may rise or fall in relation to the ambient pressure. This pressure differential has an effect on the bellows. In the case of an elevated internal pressure, the bellows may get inflated; in the case of a lower internal pressure, the bellows may collapse or may rest against the gearing rack or against other components in the vicinity of the steering gear mechanism. In the case of a movement of the steering linkage, this may cause damage to the bellows and thus leaks in the steering housing.
Although various valves are known from the prior art, through which humidity may be discharged out of a steering housing, there may also be a certain amount of compensation of volume; however, the possibilities of achieving pressure compensation between the steering housing and the environment are insufficient so as to achieve pressure compensation also in the case of a negative pressure.